In the prior art, most of the external wall, the thermal insulation, the external wall decoration of construction projects are substantially built step by step. The external wall construction requires inner/outer formwork, and the thermal insulation and external wall decoration need to set up scaffolds. There are downsides of complicated construction procedures, long construction period, and large wastes. To accommodate the requirements of 3D printing of building wall, and for printing an integrated building wall with an external wall, a reserved thermal insulating space, and an external wall decoration, the following requirements need to be met at the same time. First, the concrete slurry cannot be too thin. Thin concrete slurry is hard to set, and makes the task of ensuring the strength of the concrete difficult to accomplish. Second, the concrete material cannot be too thick. If the concrete is too thick, the fluidity becomes poor. Thick concrete material will be hard to cast, and will also affect the quality of the concrete wall. The problem that the concrete slurry cannot be too thin and the concrete material cannot be too thick is a dilemma expected to be solved.